如何访问注释属性中描述的字段

Question

是否可以访问一个字段值，其中字段名称在注释中描述，该注释在 class 中注释另一个字段。

例如：

@Entity
public class User {

    @NotBlank
    private String password;

    @Match(field = "password")
    private String passwordConfirmation;
}

注解：

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = FieldMatchValidator.class)
@Documented
public @interface Match {

    String message() default "{}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    String field();
}

现在，是否可以从 ConstraintValidator 实现中的 class 用户访问字段密码 class？

编辑：

我写了这样的东西：

public class MatchValidator implements ConstraintValidator<Match, Object> {

private String mainField;
private String secondField;
private Class clazz;

@Override
public void initialize(final Match match) {
    clazz = User.class;

    final Field[] fields = clazz.getDeclaredFields();
    for (Field field : fields) {
        if (field.isAnnotationPresent(Match.class)) {
            mainField = field.getName();
        }
    }

    secondField = match.field();
}

@Override
public boolean isValid(final Object value, final ConstraintValidatorContext constraintValidatorContext) {
    try {
        Object o; //Now how to get the User entity instance?

        final Object firstObj = BeanUtils.getProperty(o, mainField);
        final Object secondObj = BeanUtils.getProperty(o, secondField);

        return firstObj == null && secondObj == null || firstObj != null && firstObj.equals(secondObj);
    } catch (final Exception ignore) {
        ignore.printStackTrace();
    }
    return true;
}
}

现在的问题是如何获取用户对象实例并比较字段值？

Answer 1

你要么需要写一个class level constraint in which you get the full User instance passed into the isValid call or you can use something like @ScriptAssert.

目前无法将根 bean 实例作为 "normal" 字段验证的一部分进行访问。有一个 BVAL 问题 - BVAL-237 - 讨论添加此功能，但到目前为止它还不是 Bean 验证规范的一部分。

请注意，atm 无法访问根 bean 是有充分理由的。对于 validateValue 情况，依赖于可访问根 bean 的约束将失败。

Answer 2

@Hardy 然后求小费。最后写了一些符合（或多或少）预期结果的代码。

我会贴在这里，也许会帮助某人解决他的问题。

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Match {

    String field();

    String message() default "";
}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = MatchValidator.class)
@Documented
public @interface EnableMatchConstraint {

    String message() default "Fields must match!";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

public class MatchValidator implements  ConstraintValidator<EnableMatchConstraint, Object> {

    @Override
    public void initialize(final EnableMatchConstraint constraint) {}

    @Override
    public boolean isValid(final Object o, final ConstraintValidatorContext context) {
        boolean result = true;
        try {
            String mainField, secondField, message;
            Object firstObj, secondObj;

            final Class<?> clazz = o.getClass();
            final Field[] fields = clazz.getDeclaredFields();

            for (Field field : fields) {
                if (field.isAnnotationPresent(Match.class)) {
                    mainField = field.getName();
                    secondField = field.getAnnotation(Match.class).field();
                    message = field.getAnnotation(Match.class).message();

                    if (message == null || "".equals(message))
                        message = "Fields " + mainField + " and " + secondField + " must match!";

                    firstObj = BeanUtils.getProperty(o, mainField);
                    secondObj = BeanUtils.getProperty(o, secondField);

                    result = firstObj == null && secondObj == null || firstObj != null && firstObj.equals(secondObj);
                    if (!result) {
                        context.disableDefaultConstraintViolation();
                        context.buildConstraintViolationWithTemplate(message).addPropertyNode(mainField).addConstraintViolation();
                        break;
                    }
                }
            }
        } catch (final Exception e) {
            // ignore
            //e.printStackTrace();
        }
        return result;
    }
}

以及如何使用它...？像这样：

@Entity
@EnableMatchConstraint
public class User {

    @NotBlank
    private String password;

    @Match(field = "password")
    private String passwordConfirmation;
}

Answer 3

Hack around...Hack 因为这些内部 Hibernate 实现在迁移到 Java 模块时将无法工作。

@Override
public boolean isValid(final Serializable value, final ConstraintValidatorContext context) {
    var context = (ConstraintValidatorContextImpl) context;
    //no-inspection unchecked
    var descriptor = (ConstraintDescriptorImpl<Exists>) context.getConstraintDescriptor();
    var existsAnnotation = descriptor.getAnnotationDescriptor().getAnnotation();
    // Removed b/c irrelevant
}

如何访问注释属性中描述的字段

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如何访问注释 属性 中描述的字段

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如何访问注释属性中描述的字段